Question

    private void InsertLinks(IEnumerable<string> urls)
    {
        EntityDataModelContext context = DataContext.GetDataContext();
        foreach (string url in urls)
        {
            string url1 = url;
            if (context.Links.Any(l => MatchUrlHash(l.UrlHash, url1)))
            {
                continue;
            }
            Link link = new Link
            {
                Url = url,
            };
            context.Links.AddObject(link);
        }
        context.SaveChanges();
    }

    private bool MatchUrlHash(long urlHash, string url)
    {
        SHA1CryptoServiceProvider sha = new SHA1CryptoServiceProvider();
        byte[] encoded = Encoding.ASCII.GetBytes(url);
        byte[] checksum = sha.ComputeHash(encoded);
        long hash = BitConverter.ToInt64(checksum, 0);
        return urlHash == hash;
    }

How can I convert this query to something that still performs decently and doesn’t throw any NotSupportedExceptions?

Answer 1

EF doesn’t know how to build SQL query with MatchUrlHash. You can simply prepare url hash beforehand and use regular style comparison, ==.

private long CreateUrlHash(string url)
{
    SHA1CryptoServiceProvider sha = new SHA1CryptoServiceProvider();
    byte[] encoded = Encoding.ASCII.GetBytes(url);
    byte[] checksum = sha.ComputeHash(encoded);
    return BitConverter.ToInt64(checksum, 0);
}

// ...
long urlHash = CreateUrlHash(url);
if (context.Links.Any(l => l.UrlHash == urlHash))
{
   continue;
}